It doesn't get more harmless than a smile, right? Well, not exactly. A man's smile can actually make a woman more subordinate, according to new research in the Personality and Social Psychology Bulletin.

In a series of three experiments, researchers evaluated the impact of a man's smile on a woman's body language, and her perception of the man in question.

When observing a man in a dominant role (in this case, he was giving instructions), women were more inclined to like the man if he smiled — even if that smile followed an overtly sexist statement. Women were also more prone to narrow their posture when confronted with a man who smiled, rather than one who remained serious.

"It seems that overt sexism can affect behavior that actually promotes women's submissiveness when the bitter pill of sexism is given the sugar coating of a smile," researchers note.

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This troubling trend occurs in part because women are more inclined than men to rely on body language during interactions, says body language expert Patti Wood. "Even if there's dissonance between what's been said and what his body is doing, women will look to the body," she says. "If they see a smile, then the interaction seems more friendly."

It's a tricky situation, and one that highlights just how subtly sexism can intrude on interactions. The scenario is especially important at work, Wood says, because women need to stand their ground while remaining professional. Try the following tips to improve your own reactions to body language.

Know what you want: Knowing a specific goal before going into a meeting will improve your body language and communication because it minimizes any gestures, postures, or vocal expressions that are brought up by anxiety or insecurity, says Wood. For example, being focused will minimize your "ums" and fidgeting.

Watch yourself: Women in passive roles sometimes avoid eye contact, up-tone at the end of sentences, or smile more than necessary. "Smiling can make women seem more subordinate," Wood says. "If you're smiling when giving an important statement, it makes that statement weaker." Practice eye-to-eye engagement and notice if you tend to smile during important conversations.

Practice full awareness: Don't just look at what a man's body is doing—it probably doesn't give a full picture of the situation. "Think through the verbal message before you respond," Wood says. "If he says something sexist and you smile or shrink, it means he can get away with it."